Search results for "Acte"
showing 10 items of 9295 documents
New ΦBT1 site-specific integrative vectors with neutral phenotype in Streptomyces.
2016
Integrative plasmids are one of the best options to introduce genes in low copy and in a stable form into bacteria. The ΦC31-derived plasmids constitute the most common integrative vectors used in Streptomyces. They integrate at different positions (attB and pseudo-attB sites) generating different mutations. The less common ΦBT1-derived vectors integrate at the unique attB site localized in the SCO4848 gene (S. coelicolor genome) or their orthologues in other streptomycetes. This work demonstrates that disruption of SCO4848 generates a delay in spore germination. SCO4848 is co-transcribed with SCO4849, and the spore germination phenotype is complemented by SCO4849. Plasmids pNG1-4 were crea…
Whole genome sequences reveal Vibrio hemicentroti Kim et al. 2013 as a later heterotypic synonym of Vibrio splendidus (Beijerinck 1900) Baumann et al…
2017
The synonymy between Vibrio hemicentroti Kim et al. 2013 and Vibrio splendidus (Beijerinck 1900) Baumann et al. 1981 was suggested after a recent multilocus sequence analysis of the Splendidus clade, which included the type strains of both species. To clarify their status, we have determined genomic indexes from whole genome sequences of strains V. hemicentroti CECT 8714T and V. splendidus NCCB 53037T. Average Nucleotide Identities of 96.0–96.7 % and an in silico DNA–DNA hybridization value of 70.2 %, as well as similarity levels of selected housekeeping gene sequences support the consideration of V. hemicentroti as a later heterotypic synonym of V. splendidus .
Iron and Fur in the life cycle of the zoonotic pathogenVibrio vulnificus
2016
Summary In this study, we aimed to analyze the global response to iron in the broad-range host pathogen Vibrio vulnificus under the hypothesis that iron is one of the main signals triggering survival mechanisms both inside and outside its hosts. To this end, we selected a strain from the main zoonotic clonal-complex, obtained a mutant in the ferric-uptake-regulator (Fur), and analyzed their transcriptomic profiles in both iron-excess and iron-poor conditions by using a strain-specific microarray platform. Among the genes differentially expressed, we identified around 250 as putatively involved in virulence and survival-related mechanisms. Then, we designed and performed a series of in vivo …
Complete Genome Sequence of an Aquaculture-Associated Phage, FL-1, Infecting Flavobacterium spp
2017
Flavobacterium spp. are abundant and widespread in freshwater environments (1, 2). Despite the prevalence of the members in this genus, the phages infecting Flavobacterium spp. are less known. So far, most of the phages studied in detail infect fish pathogenic members of the genus, such as F. psychrophilum (3). The phage FL-1 and its Flavobacterium sp. host strain B183 were previously isolated from a water sample from a fish farm in Central Finland. Transmission electron microscopy revealed FL-1 to be a member of the family Myoviridae (4). In addition to the isolation host, FL-1 also infects multiple Flavobacterium sp. isolates and strains of the fish pathogen F. columnare, the causative ag…
Dissecting genome reduction and trait loss in insect endosymbionts
2016
Symbiosis has played a major role in eukaryotic evolution beyond the origin of the eukaryotic cell. Thus, organisms across the tree of life are associated with diverse microbial partners, conferring to the host new adaptive traits that enable it to explore new niches. This is the case for insects thriving on unbalanced diets, which harbor mutualistic intracellular microorganisms, mostly bacteria that supply them with the required nutrients. As a consequence of the lifestyle change, from free-living to host-associated mutualist, a bacterium undergoes many structural and metabolic changes, of which genome shrinkage is the most dramatic. The trend toward genome size reduction in endosymbiotic …
Origin and phylogenetic relationships of [4Fe–4S]‐containing O 2 sensors of bacteria
2018
The advent of environmental O2 about 2.5 billion years ago forced microbes to metabolically adapt and to develop mechanisms for O2 sensing. Sensing of O2 by [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion represents an ancient mechanism that is used by FNREc (Escherichia coli), FNRBs (Bacillus subtilis), NreBSa (Staphylococcus aureus) and WhiB3Mt (Mycobacterium tuberculosis). The phylogenetic relationship of these sensors was investigated. FNREc homologues are restricted to the proteobacteria and a few representatives from other phyla. Homologues of FNRBs and NreBSa are located within the bacilli, of WhiB3 within the actinobacteria. Archaea contain no homologues. The data reveal no similarity b…
Pyomelanin-producingPseudomonas aeruginosaselected during chronic infections have a large chromosomal deletion which confers resistance to pyocins
2016
When bacterial lineages make the transition from free-living to permanent association with hosts, they can undergo massive gene losses, for which the selective forces within host tissues are unknown. We identified here melanogenic clinical isolates of Pseudomonas aeruginosa with large chromosomal deletions (66 to 270 kbp) and characterized them to investigate how they were selected. When compared with their wild-type parents, melanogenic mutants (i) exhibited a lower fitness in growth conditions found in human tissues, such as hyperosmolarity and presence of aminoglycoside antibiotics, (ii) narrowed their metabolic spectrum with a growth disadvantage with particular carbon sources, includin…
Chance and necessity in the genome evolution of endosymbiotic bacteria of insects.
2017
An open question in evolutionary biology is how does the selection–drift balance determine the fates of biological interactions. We searched for signatures of selection and drift in genomes of five endosymbiotic bacterial groups known to evolve under strong genetic drift. Although most genes in endosymbiotic bacteria showed evidence of relaxed purifying selection, many genes in these bacteria exhibited stronger selective constraints than their orthologs in free-living bacterial relatives. Remarkably, most of these highly constrained genes had no role in the host–symbiont interactions but were involved in either buffering the deleterious consequences of drift or other host-unrelated function…
DNA Damage Signaling Instructs Polyploid Macrophage Fate in Granulomas.
2018
Granulomas are immune cell aggregates formed in response to persistent inflammatory stimuli. Granuloma macrophage subsets are diverse and carry varying copy numbers of their genomic information. The molecular programs that control the differentiation of such macrophage populations in response to a chronic stimulus, though critical for disease outcome, have not been defined. Here, we delineate a macrophage differentiation pathway by which a persistent Toll-like receptor (TLR) 2 signal instructs polyploid macrophage fate by inducing replication stress and activating the DNA damage response. Polyploid granuloma-resident macrophages formed via modified cell divisions and mitotic defects and not…
High prevalence and moderate diversity of Pseudomonas aeruginosa in the U-bends of high-risk units in hospital
2017
The presence of P. aeruginosa in water supply is clearly identified as a risk factor for P. aeruginosa infection in critical care units, even if routes of transmission are often unclear and remain a matter of debate. We determined here the frequency of U-bends contaminated with P. aeruginosa in high-risk units and described the population structure of this opportunistic pathogen in a non-outbreak situation. Eighty-seven U-bends from sinks of rooms in five wards were sampled 3 times and P. aeruginosa was detected in 121 of the 261 (46.4%) U-bend samples. We genotyped 123 P. aeruginosa isolates with pulsed-field gel electrophoresis and multilocus sequence typing and found 41 pulsotypes distri…